In a Universal Mobile Telecommunications System (UMTS), by means of an example including a universal terrestrial radio access for a frequency division duplex (UTRA-FDD) system, the setup of dedicated channels is implemented as illustrated in FIG. 1: A mobile user equipment (UE) sends periodically short access preambles at an increasing power level on an uplink Physical Random Access Channel (PRACH), step 11. When the user equipment receives an acquisition acknowledgement on the downlink Acquisition Indicator Channel (AICH), step 12, it sends the actual PRACH message, step 13. This message is in the following referred to as a “Resource Request”, since it is assumed that the network, in reaction to this message, allocates dedicated resources for communication between the considered user and the network. The Resource Request is forwarded on a Common Channel (CCH) over the Iub-interface from the Node B to the RNC, step 14, where a decision is taken whether or not the requested resources are granted. In case of a positive decision, the RNC selects the parameters of the dedicated resources and initiates the RL Setup procedure of the NBAP protocol, step 15. Upon reception of an RL setup response from the Node B, step 16, the RNC sends a Physical Channel Reconfiguration (or Radio Bearer Setup, or Transport Channel Reconfiguration) message on a downlink common channel, i.e. a FACH that is mapped onto a SCCPCH, to the user equipment, step 17. When this Setup or Reconfiguration message has arrived and has been processed by the user equipment, the downlink DPCCH synchronization procedure is started by the user equipment and subsequently the uplink DPCCH transmit power control (TPC) preamble is transmitted which enables the Node B to obtain synchronization on the uplink DPCCH, step 18. After expiry of the time interval employed for uplink DPCCH TPC preamble transmission, the user equipment transmits a Setup or Reconfiguration Complete message on the now established uplink DCH, step 19. The arrival of the Setup or Reconfiguration Complete message in the RNC confirms that the dedicated connection has been established successfully. The network may wait until reception of this Complete message before user data is sent in the downlink direction. The established dedicated channel can now be used for data transmission in both uplink and downlink direction, step 20.
For efficient support of packet data services, frequent switching between data transmissions on common channels, i.e. RACH/FACH, and dedicated channels, i.e. DCH on both uplink and downlink, is needed. The involved concept is referred to as channel type switching. Channel type switching consists of two different procedures: switching from common to dedicated channels (DCH setup) or switching from dedicated to common channels (DCH release).